3',6'-Bis(4-guanidinobenzoyloxy)-5-(N'-4-carboxyphenyl)thioureidospiro(isobenzofuran-1(3H),9'-(9H)xanthen)-3-one 75296-16-1 Benzoic acid, 4-((aminoiminomethyl)amino)-, 5-((((4-carboxyphenyl)amino)thioxomethyl)amino)-3-oxospiro(isobenzofuran-1(3H),9'-(9H)xanthene)-3',6'-diyl ester Bgbtsbx Fluorescein diester